Diggin' in the Garden

If you have walked around the garden lately, especially around the patio and garden office areas, you may have noticed potato-sized silver ornaments dangling from various vines and trees. These are not leftover holiday decorations! Instead, they are a form of cloning called air layering or Chinese layering--a 4000-year-old practice of vegetative propagation that originated in China.

Originally, air layering was performed by tying half of a clay pot around a wounded section of stem and then filling the container with soil or moss that was kept evenly moist. Interestingly, the only significant modifications in air layering methods have been recent changes in wrapping materials, because the technique remains a proven winner.

Unlike in other locales, here in Westwood air layering can be practiced year-round. Still, you will have the best chances for success if you begin the process in spring or late summer. You'll find most of the materials needed right in your kitchen, except for the rooting hormone. Here is the step-by-step procedure.

First, collect your equipment. You will need a very sharp knife or single-edged razor blade, rooting hormone (the same one you might use for doing cuttings), a small paintbrush, some plastic wrap or thin plastic bags that have been cut open, green moss or sphagnum moss, long twist ties, labels, and aluminum foil.
Choose a section of plant on last year's growth, or on this year's if the stem is rigid (woody or lignified) and has some bark. Choose plant materials that are healthy and look like specimens you would be proud of when the rooted cutting is removed from the mother plant.
On a section somewhat below a node, completely girdle the stem, making a strip one-half to one inch long. Carefully peel away the bark, and then scrape the exposed tissue to remove all phloem and vascular cambium. This ensures that the plant cannot heal itself instead of making roots.
With the paintbrush, coat the cut section with rooting hormone powder.
Tear off a sheet of plastic wrap about ten to twelve inches long, and have two twist ties ready. Moisten your sphagnum moss, and grab several handfuls to make a ball about the size of a potato, compressing it to release excess moisture.
Split the sphagnum ball in half, and place the two halves around the girdled section of stem. Holding this firmly, without twisting, wrap the plastic sheet around the sphagnum, and tie one end with a twist tie. Now squeeze out excess water and air, leaving a firm ball centered over the girdled section, before finishing the package with the second twist tie.
Cover the plastic loosely with aluminum foil, somewhat open on the lower side, to form a light reflector on three sides. This will create a cool, dark environment suitable for root growth.
Finally, attach a label to the stem to remind yourself when the air layer was begun.

Now you just have to wait, but remember never to let your moss dry out, even if you have to open up the package to add water. The time required ranges from two to three weeks to as long as two years, depending on the plant species. You'll know that you have succeeded when you observe roots growing through the sphagnum. Then you can carefully remove the covering, sever the root cutting, and pot the new plant in a good soil mix.

A variety of plants have a history of success with this technique, including species of Ficus, Croton, Monstera, Philodendron, Citrus aurantifolia, and litchi. Additionally, quite a number of tropical and subtropical trees and shrubs respond nicely to air layering, as do temperate species of Berberis, Erica, Rhododendron, Magnolia, and Cornus. Araliaceae are also good candidates for air layering. But don't feel limited-try everything. If you are a beginner, though, consider selecting a plant that you can work without using a ladder, and save balancing on a ladder for when you have mastered the procedure!

RAND PLEWAK (Garden Manager)

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